1. Field of Invention
The invention relates to a structure for a machining center. The invention concerns more specifically a lathe which comprises two devices, each for support and for driving in rotation a workpiece to be machined about a control axis, the control axes of these devices being aligned according to an axis, referred to as the first axis, and the said devices being, on the one hand, separated by a predetermined distance, and, on the other hand, being opposing, i.e. oriented so as to bring about an operation of taking, by one of the devices, of a workpiece driven by the other device.
2. Description of Related Art
Conventionally, a machining center comprises a frame, and each device for support and for driving in rotation a workpiece to be machined about a control axis is called a headstock, and consists of a device comprising:
a rigid support connected to the frame of the machine,
a workpiece spindle rotary mounted on this rigid support,
a motor for driving the spindle in rotation.
In the following description, each device for support and for driving in rotation a workpiece to be machined about a control axis will be designated by the simplified expression xe2x80x9cworkpiece support device.xe2x80x9d
Conventionally, one of the two workpiece support devices (referred to as the accessory device) is movable relative to the other (referred to as the main device), and more specifically, is borne by a device for control and for displacement toward this main workpiece support device in such a way as to bring about an operation of taking of a workpiece which has already been machined, this taking operation being carried out while the workpiece is being driven in rotation by the said main workpiece support device.
Because it has to be displaced, and rapidly displacedxe2x80x94all the more so in order to affect as little as possible the duration of the machining cyclexe2x80x94the accessory workpiece support device is selected in such a way as to have a mass that is less than that of the main workpiece support.
Selection of a workpiece support of lesser mass has a notable effect on the mechanical output power of this device and on its capacity to achieve the driving of a workpiece in rotation to allow machining operations requiring a lot of force.
There exist a number of machines of this type, the machining possibilities of which are affected by too low an output power for an accessory workpiece support device.
A result which the invention aims to obtain is in particular a machining center having workpiece support devices which, while allowing the operations referred to as taking, have appreciably the same mass and the same output power so as not to affect the productivity.
Another drawback of known machines is that the control of the displacement of the accessory workpiece support uses a slide which must be protected from particles by an appropriate device.
The protection devices used are generally of the collapsible type, and the length of the displacement of the accessory workpiece support device renders their construction relatively complex.
Another object of the invention is, in particular, simplification of the construction of the collapsible protection device.
Also an object of the invention is a machine having a structure with an increased resistance to elastic deformation.
Other results obtained by the machine according to the invention will be mentioned in the following.
The invention has as its subject matter a machine of the initially mentioned type, in particular wherein
each of the two workpiece support devices is supported by a device for control and translatory displacement along a first axis, the said control and translatory displacement devices being actuated in such a way that each of the workpiece support devices movable between a position of maximal distance from the opposite support device and a position of maximal bringing closer together with this opposite workpiece support device, the sum of the ranges of possible displacements of the two devices being at least equal to the distance which separates the two workpiece support devices when they are placed in their maximal spaced apart position,
the main device for holding and for displacement of at least one machining tool is disposed in such a way as to bring about the displacement of this tool at most in a plane which, on the one hand, is orthogonal to the first axis and, on the other hand, is situated between the two workpiece support devices in such a way as to bring about a machining of a workpiece borne by at least one of these workpiece support devices.
The invention will be better understood from reading the description which follows, given by way of non-limiting example, with reference to the attached drawing: